Remove commment about java.nio.charset.ModifiedUtf8

java.nio.charset.ModifiedUtf8 is unused and removed.

Test: treehugger
Change-Id: I650c0bee5066c3bc2ca4bd8a845ee7d6f88faea2
diff --git a/dx/src/com/android/dex/Mutf8.java b/dx/src/com/android/dex/Mutf8.java
index c64da33..df3f315 100644
--- a/dx/src/com/android/dex/Mutf8.java
+++ b/dx/src/com/android/dex/Mutf8.java
@@ -21,8 +21,6 @@
 
 /**
  * Modified UTF-8 as described in the dex file format spec.
- *
- * <p>Derived from libcore's MUTF-8 encoder at java.nio.charset.ModifiedUtf8.
  */
 public final class Mutf8 {
     private Mutf8() {}